天山北坡改良草地凋落物混合分解特征研究

研究凋落物分解过程及其调控机制对于预测生态系统凋落物分解、揭示营养元素循环规律具有重要意义。本试验采用野外凋落物网袋分解法，设置了紫花苜蓿（Medicago sativa）和无芒雀麦（Bromus inermis）不同混合比例的叶凋落物处理，在分解1个月、3个月和12个月后取出测定凋落物剩余量及碳氮含量。试验结果表明：单独紫花苜蓿凋落物的分解和碳、氮释放量均高于无芒雀麦凋落物单独分解，混合凋落物剩余率介于两种单一凋落物分解剩余率之间；混合凋落物紫花苜蓿和无芒雀麦凋落物比例为1：3的组合表现为显著的协同效应，其他组合为加和效应；凋落物剩余率及碳氮元素的剩余率与其初始氮含量呈负相关关系，与初始碳氮比呈正相关关系。研究结果表明，在新疆山地草原生态系统，凋落物混合分解效应与其组合比例密切相关，在豆禾凋落物适宜比例下混合凋落物分解可产生协同效应。

Decomposition Characteristics of Mixed Litter on the Improved Grassland on the Northern Slope of the Tianshan Mountains

Studying the decomposition process of litter and its regulation mechanism is of great significance for predicting the decomposition of litter in the ecosystem and revealing the circulation of nutrient elements. We explored the decomposition rates and nutrient dynamics of single and mixed-species litter,the litter-mixing effect and the effect of component litters in a mixture on decomposition. The field-litter bag experiment was used in this study,to study the litter decomposition and nutrient dynamic change of leaf litter;five mixture proportions treatments were set up. Litter bags were collected after 1,3 and 12 months,and the mass loss,carbon (C) and nitrogen (N) content in the remaining litter were determined. The results indicated that:pure Medicago sativa litter decomposed faster than Bromus inermis litter,the decomposition rate of mixed litters was between that two single-species litter. The litter mixture with (1 to 3) Medicago sativa and Bromus inermis had synergistic effect while the other mixture proportions had additive effects. The percentage of final litter mass remaining,as well as carbon and nitrogen remaining,was negatively related with initial litter N content while positively related with carbon to nitrogen ratio. Our results show that litter component has significant effects on litter decomposition,and mixing litter at an appropriate ratio of legume litter produced a synergistic effect.